The present invention relates generally to optical lens assemblies and more particularly to a mounting mechanism for a system having lens members which are movable relative to each other.
In a conventional lens system, there are provided front and rear lens assemblies which are movable relative to each other. Such a system will include an inner lens barrel in which a front lens assembly is mounted and an outer lens barrel in which a rear lens assembly is mounted. Normally, the lens assemblies are fixedly mounted within the barrels and the inner lens barrel is movably fitted within the outer barrel which may be permanently or detachably mounted on the housing of an optical instrument such as a camera. The outer barrel may be provided with a pair of annular support projections which extend inwardly thereof and upon which the inner barrel may bear during axial movement thereof relative to the outer barrel in order to effect focusing operation.
In order that a mounting mechanism for such a lens assembly enable the performance of high speed movement with uniformity of operational force over the entire focusing range of the lens system, it is normally required that the inner and outer lens barrels be produced with very close manufacturing tolerances. It is well known in the art of machining such systems that when eccentricity or out-of-roundness of the barrels must be limited to specific and ideal values during the manufacturing thereof, production efficiency will be greatly decreased and production costs will significantly increase.
In order to further improve the smoothness of the sliding movement which must occur between the inner barrel and the outer barrel, other techniques may be employed. However, such other techniques have been found to be incompatable with improving the out-of-roundness of the elements. It is, therefore, virtually impossible to manufacture in inner and outer lens barrels in an economical manner while at the same time maintaining the eccentricity or out-of-roundness which arises to tolerances of such close values that sufficiently accurate and reliable control of focusing of the optical system may be accomplished while at the same time maintaining the operative forces involved constant over the focusing range.
In the case of zoom optical systems, conventional mounting mechanisms will give rise to similar unsolved problems particularly between the variator and/or compensator support barrel and the stationary barrel or a cam tube having zoom control cam slots. When the sliding surfaces of such barrels are finished by a lapping or rubbing operation or the like, in order to render the mechanism uniformly easy to operate from any desired position, there will occur a higher possibility of shifting of the optical axis of the zoom lenses thereby giving rise to misalignment relative to the relay lens during zooming.
A further problem which arises involves the fact that an outer stationary and an inner movable barrel must be machined by boring and milling operations, respectively, and as a result a great number of successive minute ridges will be formed on the facing surfaces of the inner and outer barrels. This will cause a disagreeable or undesirable feel and noise characteristic to occur when the inner barrel is moved relative to the outer barrel.
Accordingly, it is an object of the present invention to provide an economical approach in forming the operational mechanism for housing and operating an optical system involving relatively movable lens elements by compensating for deficiencies in the manufacture of the separate elements of the mechanism while nevertheless permitting operation of the movable lens element to be capable of accomplishment in a uniform manner with ease by an operator.
A further object of the invention is to provide a mounting device which will overcome the drawbacks of conventional systems and which will provide a lubricating device at the interface between an inner movable barrel and an outer stationary barrel of such a mechanism.
A further object of the invention is to provide a mounting mechanism for a telephoto or zoom optical system wherein the front component is movable for focusing or zooming, the remaining rear component being stationary during focusing or zooming, the mechanism comprising an inner barrel within which a front component is held and an outer stationary barrel or cam tube within which the rear component is held, with sliding mobility of the inner barrel relative to the outer barrel being enabled at a faster rate than would otherwise be possible while at the same time achieving improvement in the reliable operation of the overall optical system.
A further object of the invention is to provide a device for assuring improvement of reliable operation of an optical system while maintaining a satisfactory state of roundness between the inner and outer barrels by enabling omission of a rubbing or finishing step which has been heretofore necessary in order to impart a desired mobility into the operational mounting.
A further object of the invention is to provide an operational mechanical mounting for an optical system which will reduce or eliminate noisy operation which would otherwise occur by frictional engagement between the inner and outer barrels when they are moved relative to each other.